The present invention generally pertains to injection molding of cable ties, and is particularly directed to methods that facilitate removal of a cable tie from the mold parts.
A cable tie may be used for bundling together articles such as cables or the like by forming and locking a closed loop around the articles. Cable ties also have other uses. Cable ties are also known as cable straps, cable clamps, cable clips, bundling ties, bundling straps, bundling clips, bundle ties, bundling belts, wire ties, ring clamps, adjustable clamps, harnessing devices, strap seals, binding straps, and ties. A cable tie includes a locking head, a strap extending from the head and terminating in a tip for passing through an opening in the head, and ratchet teeth on at least one side of the strap, wherein the locking head includes a pawl having teeth with surfaces for engaging the ratchet teeth to lock the strap in the locking head after the tip end of the strap has been pulled through the opening in the head. A cable tie may or may not include additional components; and the strap may have two or more sides, one, some or all of which include ratchet teeth. Examples of cable ties are described in U.S. Pat. Nos. 3,739,429; 3,924,299; 3,965,538; 4,473,524; 4,573,242 and 5,372,773.
Cable ties are manufactured economically by a cyclic injection molding method, in which molten plastic material is injected into a mold cavity defining the cable tie and then allowed to solidify within the mold cavity. The mold parts defining the mold cavity are then separated and the cable tie is removed from the mold parts. A preferred plastic material for cable ties is nylon, although other plastic materials may be used.
One method of injection molding a typical cable tie, as described above, that facilitates removal of the cable tie from the mold parts is described in U.S. Pat. No. 5,372,773. Such method includes the steps of:
(a) forming the cable tie by injecting molten plastic material into a mold cavity defined by a first mold part combined with a second mold part, wherein the first mold part includes a head region defining a portion of the head of the cable tie and the second mold part includes a tip region defining a portion of the tip of the cable tie;
(b) separating the first mold part from the second mold part while retaining said portion of the head of the cable tie in the head region of the first mold part and said portion of the tip of the cable tie in the tip region of the second mold part, to separate the head from the second mold part, to separate the tip from the first mold part, and to separate a major portion of the strap of the cable tie from the first and second mold parts;
(c) further separating the first mold part from the second mold part while still retaining said portion of the head of the cable tie in the head region of the first mold part to thereby remove said portion of the tip of the cable tie from the tip region of the second mold part; and
(d) subsequent to step (c), removing the head of the cable tie from the head region of the first mold part.
The present invention provides a method of injection molding a cable tie having a locking head, a strap extending from the head and terminating in a tip for passing through an opening in the head, and ratchet teeth on at least one side of the strap, wherein the locking head includes a pawl having teeth with surfaces for engaging the ratchet teeth to lock the strap in the locking head after the tip end of the strap has been pulled through the opening in the head, the method comprising the steps of
(a) forming the cable tie by injecting molten plastic material into a mold cavity defined by a first mold part combined with a second mold part, wherein the first mold part includes a tip region defining a portion of the tip of the cable tie and a head region defining a portion of the head of the cable tie, and said mold parts further define a strap region for forming a portion of the strap that extends between the head and the tip of the cable tie;
(b) separating the first mold part from the second mold part while retaining said portion of the tip in the tip region of the first mold part, said portion of the head in the head region of the first mold part and a portion of the strap in the strap region of the second mold part, to remove the tip from the second mold part, to remove the head from the second mold part, and to remove portions of the strap from the first mold part; and
(c) removing said retained portions of the cable tie from the mold parts.
Additional features of the present invention are described with reference to the detailed description of the preferred embodiments.